Two-temperature fuel oil burner supply systems



TWO-TEMPERATURE FUEL OIL BURNER SUPPLY SYSTEMS Filed Feb. 3, 1964 July27, 1965 w. J. TRABILCY 2 Sheets-Sheet 1 WILL/AM J. TRAB/LCY BY MMQ MATTORNEYS July 27, 1965 w. J. TRABILCY 3,196,925

TWO-TEMPERATURE FUEL OIL BURNER SUPPLY SYSTEMS Filed Feb. 3, 1964 2Sheets-Sheet 2 o 8 -IO T m a g) E INVENTOR FIG. 4

W/LL/AM J. TRAB/LCY WQMQM ATTORNEYS United States Patent 3,196,925TWll-TEh HPERATURE FUEL OIL BURNER SUFPLY SYSTEMS William J. Trabiley,280 Prospect Ave, Hackensack, NJ. Filed Feb. 3, 1964, Ser. No. 341,93514 tClaims. (Cl. 158-36) The present invention relates to fuel oilburner supply systems and is particularly concerned with systems forhandling the temperature-controlled delivery of preheated viscous fueloils, such as No. 6 grade, to oil burning equipment.

The change over the past ten years to refinement of crude petroleum bycatalytic cracking processes has had a significant effect on theoperation of fuel oil burner supply systems which handle high viscosityoils such as No. 6' grade fuel oil sometimes called Bunker C. In theseburner supply systems the fuel oil is stored in a tank which is usuallyunderground, and the stored oil is drawn from the tank by pumps whichsupply the fuel under pressure through preheating units for delivery tothe burner equipment. The preheating units heat the fuel to the desiredburning temperature for obtaining efficient and complete combustion. Theamount of fuel oil delivered by the pumps and heated by the preheatingunits normally is about double the maximum burning rate of the burnerequipment in the system so that there is always a predetermined amountof excess hot oil heated to the burning temperature.

Conventionally, this heated excess oil is returned to the storage tankin close proximity to the inlet end of the pump suction line in the tankto mix with the cold viscous tank oil and bring it to a flowable andpumpable temperature which is approximately 120 F. 'A typical system ofthis type is described in United States Letters Patent No. 2,802,520,issued August 13, 1957, to William I. Trabilcy and entitledTransportation System for Viscous Liquids.

As a result of the presently used catalytic refining processes, it isnecessary to heat the fuel oil to considerably higher temperatures thanever before in order to assure satisfactory and substantially completecombustion. Thus, the temperature of excess unburned hot oil beingreturned to the storage tank to render the cold tank oil fiowable andpumpable is higher and thus heats the cold stored oil to a highertemperature. A conventional system is adjusted to operate satisfactorilyunder these conditions when the burning equipment is being fired at itsmaximum rates. However, serious operational difiiculties are encounteredwith multiple burners particularly when there is a reduction in theburning rate or when one or more of the burners being supplied is shutdown. When this happens, more hot oil is returned to the storage tank tofurther increase the temperature of the mixed suction oil. Thiscondition of over-heated suction oil temperatures at the relatively lowpump suction pressure objectionably promotes vaporization of the suctionline oil with the result that oil flow is interrupted, and burnerfailure ensuingly occurs. Such burner failures are especially dangeroussince they frequently result in explosion or burner puff-back.

Owing to the present refinement practices, objectionable overheating ofthe fuel oil pump suction due to variations in load conditions hasbecome so prevalent in the conventional supply systems that it hasprompted the relocation of the hot oil return outlet to a region in thestorage tank considerably remote from the suction line inlet. While thischange permits the objectionable heat of the hot return oil to bedissipated, it is, at the same time, a waste of energy and usuallyrequires that additional heating means, such as, for example, a steamheating coil, be placed in the tank to bring the cold stored oil up to apumpable temperature.

The present invention contemplates and has as its major object a novelfuel oil temperature control system which prevents overheating of thesuction line oil regardless of load conditions and without deliberatedissipation or loss of heat.

More specifically, it is an object of the present invention to provide anovel oil temperature control system wherein the flow of the preheatedunburned oil returned to the storage tank is thermostatically controlledin response to the oil temperature at the pump suction or discharge toprevent the oil drawn from the tank from being objectionably overheated.Thisis essentially accomplished, in accordance with the presentinvention, by placing a thermostatically controlled valve in a hot fueloil return line and passing at least substantially all of the unburnedpreheated pump discharge oil through the valve so that the rate ofreturn oil flow is regulated thereby.

A further object of the present invention is to provide a noveltwo-temperature viscous fuel oil burner preheating system which isespecially adapted to handle No. 6 grade fuel oil without objectionablyoverheating the suction line oil.

Still a further object of the present invention is to provide a noveltwo-temperature viscous fuel oil burner supply system wherein the coldstored fuel is heated to burning temperature in two stages and'whereinonly a sufiicient amount of oil is heated to burning temperature in thesecond stage to equal the burning rate and to heat cold stored oil to acontrolled pumpable temperature.

Further objects will appear as the description proceeds in connectionwith the appended claims and annexed drawings wherein:

FIGURE 1 is a partially diagrammatic view illustrating one embodiment ofthe two-temperature preheating system of the invention;

FIGURE 2 is a diagrammatic view of piping details at the fuel oilburners being supplied with the system shown in FIGURE 1;

FIGURE 3 is a fragmentary diagrammatic view of another embodiment of thepresent invention;

FIGURE 4 is a partially diagrammatic view of still another embodiment ofthis invention; and

FIGURE 5 is an enlarged fragmentary longitudinal section of thethree-way thermostatically controlled valve illustrated in FIGURE 4.

In the embodiment of the invention shown in FIGURE 1, fuel oil iswithdrawn from a storage tank 11 and supplied to one or more oil burnerassemblies of which there are two indicated at 12 and 13 respectively. 1So far as the invention is concerned, there may be any number of oilburner assemblies including only one.

Storage tank 11 is of conventional construction and usually is buriedbelow the surface of the ground outside of a building in which burners12 and 13 are disposed. The oil used in buildings larger than domesticdwellings such as, for example, public schools and most industrialplants, is the relatively viscous type known as Bunker C or No. 6 gradewhich flows slowly especially when the tank temperature is about 50 F. m

Supplying burners 1.2 and 13 with fuel oil under pressure is a remotepump set 16 which draws fuel oil from storage tank 11 through a suctionline generally indicated at 13. Suction line 18 comprises a suction stubpipe 20 connected by a T-fitting 21 to a supply conduit 22 made up ofsuitable pipe sections and leading to pump set 16 located in the boilerroom. Conduit 22 preferably contains a check valve 24 to prevent reverseflow back to tank 11. Suction pipe 20 extends downwardly through adetachable manhole cover 23 on tank 111 and has an open lower endprojecting into a conventionally constructed bell 25 on the bottom oftank 11. A heater 36 in stub 20 may be energized in any suitable manner.

Pump set 16 comprises two conventionally constructed oil pumps 39 and 40having inlets respectively connected to supply conduit 22 in parallelrelationship by branch lines 42 and 4-4 which contain manual shut-offvalves 46 and 47 respectively. The discharge sides of pumps 38 and 40are respectively connected in parallel to an oil discharge pipe section48 by branch lines 50 and 52. Each branch line 50 and 52 contains amanual shut-off valve 54 and a check valve 56, the latter valve beingefiective to permit flow into line 48 and to block return flow of oil tothe discharge side of each of the pumps. With this piping arrangement,either pump 39 or pump 40 may be operated while the other is inactive,or both pumps may be operated at the same time.

Pipe section 48 has an upwardly extending open end 62 received in anair-separation chamber 63 defined by a cylindrical housing 64 having atop air and oil outlet port 65 and a side oil supply port 66. Oildelivered by pump set 16 flows into chamber 63. There, any entrained airseparates from the cascading oil and exits through outlet port 65 forreturn to tank 11 in a manner to be presently described. Thus, airbubbles or pockets entrained in the pumped oil will separate from theoil which otherwise substantially fills chamber 63 causing the separatedair to rise upwardly to port 65.

Oil pumped into chamber 63 flows through outlet port 66 which isconnected by a pipe section 68 to an inlet 70 of a low density electricimmersion heater assembly 72. Heater assembly 72 is of conventionalconstruction and essentially comprises a hollow metal tubular casing 7 4of larger diameter than the piping connected thereto and through whichoil flows in contact with end mounted electrical heater elementsdisposed in casing 74 and indicated generally at 76. Casing 74 isprovided with a hot coil outlet 78. Additional low density conversionheaters (not shown) may be provided in series with heater assembly 72 ifneeded;

Each set of heater elements 76 is separately energized by current from amain electric source passing through a normally closed manual disconnectswitch 79 and an adjustable thermostatic unit 80 having a control dial81 for selecting the temperature to be imparted to the oil. The heaterelement sets 76 and associated units 80 are preferably mounted on outerflanges 82 and 83 so that the circuits may be electrically separate atthis region.

In practice, the thermostatic units 80 are set to open the electricalcircuits de-energizing their respective heater element sets 76 when theoil temperature reaches approximately 180 F. and to close the electricalcircuits when the oil temperature drops below approximately 175 F. As aresult, the temperature of oil flowing through the heater assemblyoutlet 78 for delivery to burners 12 and 13 is usually maintained withinthe range of approximately 160 F. to 200 F. which is satisfactory forassuring substantially complete combustion.

With continued reference to FIGURE 1, outlet '78 of heater assembly 72is connected to a burner feed line 86. Feed line 86 is connected toburners 12 and 13 by fluid branch conduits 88 and 90 respectively tothus furnish burners 12 and 13 with a continuous supply of heated oil.Contained in lines 88 and 90 respectively are manual valves 91 and 92for selectively permitting and blocking oil flow to burners 12 and 13.

Burners 12 and 13 are each of conventional construction for burning No.6 grade fuel oil and may be either of the gravity (non-pump) or pumptype. In the present embodiment (as shown in FIGURE 2), the burners areof the pump type each having a continuously running pump 93 in a feedline 94, a control valve 95 downstream of pump 93 for controlling theflow rate of oil to the burner nozzle (not shown), a solenoid operatedburner shut-off valve 96 downstream of valve 95, and a tailpiece heater97 upstream of shut-ofl valve 96 for heating oil at the burner onstart-up. Valves 95 and 96, pump 93 and tailpiece heater 97 are allstandard parts of burners equipped 4 to handle No. 6 grade fuel oil andtherefore need not be described further.

With continued reference to FIGURES l and 2, burners 12 and 13 arerespectively provided with recirculating lines 93 and 99 each containinga check valve 100. Recirculating lines 98 and 99 are normally connectedto their respective burner feed lines 94 between burner pump 93 andcontrol valve 95 for returning oil to line 86. Thus excess unconsumedoil delivered by the burner pumps 93 is returned through lines 98 and 99to line 86 for mixture with oil delivered by pump set 16 andrecirculation through branch lines 88 and 90. It will be noted that, inaccordance with the present invention, excess unconsumed hot oil atburners 12 and 13 resulting from throttling of control valve 95 orclosing valve 96 is not returned to the storage tank 11 but rather isrecirculated back to the inlets of the burners.

Feed line 86, as shown in FIGURE 1, contains a T- fitting 101immediately downstream of heater assembly outlet 78 and upstream fromthe connection of branch conduits 88 and 90 to line 86. Connected tofitting 101 is a burner by-pass return line 102 which is joined at itsopposite end to a T-fitting 104 in an oil storage tank return line 106.Excess hot oil delivered by pump set 16 through heater assembly 72 andnot burned by burners 12 and 13 flows through line 102 and into line 106for return to tank 11.

In accordance with the present invention, line 102 contains athermostatically controlled flow regulating valve 108 disposed betweenfittings 101 and 104. Valve 108 preferably is a conventional normallyopen self-powered modulating type needle port valve through which flowof oil is controlled by a suitable thermostatic element comprising atemperature responsive fluid filled bulb 110 inserted into a T-fitting112 contained in suction line 18. Bulb 110 is connected to valve 103 bya capillary tubing 114 and may be located anywhere in the oil supplylines upstream from the inlet 70 of heater assembly 72. Advantageously,bulb 110 is located in suction line 18 to accurately sense thetemperature of oil drawn from tank 11.

According to the present invention, valve 108 is responsive to the fueloil temperature sensed by bulb 110 to vary the flow rate of oil beingreturned through line 102 inversely with respect to the oil temperature.Thus, as the oil temperature increases toward F., valve 108 responds toreduce the flow rate of oil through line 102. Conversely, as the oiltemperature sensed by bulb 110 decreases, control valve 108 will openwider to permit a greater flow of hot oil to return line 106.

With continued reference to FIGURE 1, return line 106 is provided with avertical pipe section 116 extending downwardly through manhole cover 23and having an open lower end projecting into suction bell 25 in closeproximity to the inlet end of suction pipe 20.

Suction bell 25 is of standard construction and serves two importantfunctions. One is to limit the heat loss by confining the return hot oilwithin the bell. The other is to serve as a mixing or blending chamberwhere the return hot oil is mixed with cold viscous tank oil flowinginto the bottom of the bell to replace the oil consumed by the burneroperation. In this way, the contents of tank 11 outside of hell 25remain at substantially the temperature prevailing outside the tankwhile the liquid fuel oil in the bell is at an elevated temperaturesuitable for pumping. With the system thus far described, as long aspump set 16 continues to operate, heater assembly 72 normally suppliessubstantially all the heat required to bring the oil flowing to burners12 and 13 up to the desired temperatures. After start-up, the heatrequired to bring cold tank oil flowing into bell 25 up to the desiredpumping temperature of about 120 F. is supplied by the hot return oilflowing through line 102 and 106. During stand-by periods when the pumpset 16 is not operating, the fuel oil supply and return lines areadvantageously electrically heated by the electrical system described inthe previously mentioned Patent No. 2,802,520 or by any other suitablemeans such as conventional steam heating means. This keeps the oil inthe supply system warm and flowable for quick, easy and dependablestarting.

Particularly where high pressures are used, line 152 preferably containsa pressure reducing valve 126 between valve 198 and T-iitting 101 toprovide a low pressure drop across valve 108. This renders the responseof valve 108 more sensitive to small oil temperature changes and assuresa smoother operation in the control of the amount of hot oil returned totank 11. Pressure reducing valve 126 may be of any suitable type.

With continued reference to FEGURE 1, the air separator outlet port 55is connected by a conduit 123 to fitting 104% in return line 1%. Airseparated in chamber 63 passes through port 65, conduit 128, and line106 into storage tank 11. Under conditions especially where valve 108 isoperated to reduce the flow rate of hot return oil through line 102, theexcess oil flows through conduit 128 for return to tank 11. A pressureregulating valve 150 contained in conduit 128 is set to maintain the oilbeing supplied to burners 12 and 13 at a desired pressure. It is clearthat the oil returned through conduit 128 is not heated to an elevatedtemperature by preheater 72. In-

ead, the temperature of return oil flowing through conduit 128 is nohigher than the temperature of oil drawn through suction pipe 20, andthe temperature of this oil is controlled, during normal runningperiods, by the operation of valve 105.

With continued reference to FIGURE 1, emergency pressure safety reliefvalves 135 and 138 are connected to the discharge sides of pumps 38 and49 respectively. The outlet ports of release valves 136 and 138 areconnected by a common pipe section 141 to conduit 123 downstream ofvalve 130. Valves 136 and 133 are normally closed pressure responsivevalves that open only when the oil pressure increases beyond apredetermined limit, as caused by, for example, a line blockage to thusrelieve the system of excessive oil pressure by by-passing the oil fromeither or both pump outlets to conduit 128 for discharge to tank 11through return line 166.

in starting up the oil burner supply system shown in FIGURE 1, heaterassemblies 35 and 72 are energized and either or both pumps 39 and 40are started. Cold tank oil in suction pipe 25 is heated to a flowableand pumpable temperature of about 120 F. by heater rod 36. Normally, thetemperature of oil stored in tank 11 corresponds to temperature of theground (about 50 F.) in which tank 11 is buried. The cold oil standingin suction pipe 20 is heated by heater 55 to a pumpable 120 temperatureand then is withdrawn by pumps 39 and/or 40 and discharged intoseparation chamber 63 where entrained air is separated and returned totank 11 through port 65.

With excess oil, the air-free oil discharged from the separation chamberoutlet port 56 is passed under pump pressure through heater 72 whichraises the temperature of the oil to about 180 F. Although the oil insupply line 85 is very hot, it will not vaporize owing to the pumpdischarge pressures. This hot preheated oil is then supplied to burners12 and 13 through lines 88 and 5d. The capacity of each of the pumps 39and 40 is such that the amount of oil supplied thereby is substantiallyfixed and about double the maximum burning rate of burners 12 and 13.Thus, when burners 12 and 13 are being fired at their maximum rate,there will always be an excess quantity of oil which is passed throughand heated by heater assembly 72. This excess unburned hot oil, insteadof being delivered to burners 12 and 13, is by-passed through line 102and control valve 103 for return to storage tank 11 through line 106.

The excess oil returning through line 1% mixes with cold tank oilentering suction bell 25 to elevate the temperature of the oil beingwithdrawn through suction pipe 20 to a pumpable temperature of about 120F. After preheated oil has begun to return to suction bell 25 throughline 102 to heat cold stored oil to pumpable temperature, heater 36 willautomatically deenergize, especially to prevent overheating of oil inthe suction line to avoid vapor lock in the oil pumps 39 and 40.

Responding to the oil temperature sensed by thermostatic bulb 110, valve108 is automatically actuated to control the flow rate of hot excess oilreturning to tank 11 through line 102. Thus, if the oil temperaturesensed by bulb rises above F., valve 103 will close. The excess oildelivered by pumps 3% and 40, instead of flowing through heater assembly72, will pass through separation chamber 63, through conduit 123 andthrough return line 106 to suction bell 25 in storage tank 11. Thisreturn oil will lose some heat in returning to tank 11 and, as a result,the temperature of oil at the discharge sides of pumps 39 and 40 willbegin to decrease.

Upon sensing a temperature decrease, thermostatic bulb 110 will causevalve 108 to open, thus increasing the flow rate through line 102 anddecreasing the flow rate through conduit 128. The further valve 108 isopened, the lower the flow rate through conduit 1128 becomes. As aresult, oil at a higher temperature is returned to suction bell 2.5 toincrease the temperature drawn through suction pipe 20.

When one of the burners 12 or 13 is shut down, or when the firing rateof burners 12 and 13 is reduced, pumps 39 and 40 continue to deliver thesame amount of fuel oil. With the reduction of burning rate, the flow ofoil through valve 10% remaining the same, hot preheated oil willincrease. If this condition were allowed to persist, the temperature ofthe oil in suction line 18 would become so hot that it would eventuallyvaporize under the low pump suction pressure. Such vaporization andconsequent pump vapor lock would interrupt the steady flow of oil toburners 12 and 13, causing burner failure and possible explosion orpuff-back.

With the present invention, however, the increasing oil temperature issensed by bulb 110 before entering heater 72. As a result, valve 108will respond by closing to reduce the flow rate through line 102 andthus reduce the amount of heated oil being returned to bell 25.

In this manner, valve 108, in responding inversely to the oiltemperature sensed by bulb 110, regulates the flow of heated return oilto maintain a suitable oil pump suction temperature of approximately 120F. As a result the objectionable condition of suction line oil vaporlock is overcome without wastefully dissipating any heat and thusrendering the system very economical to operate. Thus, the inventionprovides a dependable, easily started, two-temperature fluid system.

The embodiment illustrated in FIGURE 3 is the same, with one exception,as embodiment of FIGURE '1, and to the extent that both embodiments arealike, like reference numerals have been used to identify like parts.

In the embodiment of FIGURE 3, burner lines 98 and 99 are connected toan oil purge line and respectively contain orifices 151 and 152. Purgeline 150 is connected by a T-fitting 154 to return line 106 downstreamfrom T-fitting 104.

Orifices 151 and 152 permit very small amounts of hot oil to circulatethrough lines 88 and 90, through the burner piping, and through lines 98and 99. This prevents the fuel oil from objectionably cooling off incold un heated parts of the piping around the burners especially duringstand-by periods. The amount of oil which orifices 151 and 152 permit toflow through line 150 is very small and not enough to cause anyobjectionable effect on the temperature of the oil in hell 25 or suctionpipe 20. Line 150 is advantageously employed during cold start-ups whenthere may be the likelihood that collected oil has objectionably beencooled in unheated piping at the burners.

The upstream pressure maintained by valve 130 in line 128 and also inline 102 upstream from valve 126 depends upon the type of burnersemployed in the system such as, for example, the pump-type burnersillustrated in FIGURE 2 or the gravity-type burners illustrated inFIGURE 1. Normally, an upstream pressure of about 80 p.s.i. is requiredfor gravity-type burners. Valve 130 is adjusted to regulate pressure tomaintain a sufiicient downstream pressure for overcoming pipe linefriction resulting from oil flow to tank 11. Usually, valve 139 isadjusted to reduce line fluid pressure to about to psi. Valve 126 isadvantageously adjusted to provide a line fluid pressure at the inlet tovalve 108 which is approximately equal to the line fluid pressure on thedownstream side of valve 130 to provide a low pressure drop across valve108 as previously described.

FIGURE 4 illustrates a preferred embodiment of this invention wherein athree-way thermostatically controlled valve 160 of conventionalconstruction is employed in place of valves 108 and 126. To the extentthat the construction shown in FIGURE 4 is like the previous embodimentsillustrated in FIGURES 13, like reference numerals have been used toidentify like parts.

As shown in FIGURE 4, the air separator comprising chamber 63 in theconstruction of FIGURE 1, has been omitted, and discharge pipe section48 is connected directly to a T-fitting 162 contained in a fluid conduit164. One end of conduit 164 is connected to inlet 70 of heater assembly72.

With reference now to FIGURES 4 and 5, valve 160 is shown to comprise ahousing 166 having axially opposed inlet ports 168 and 170 and an outletport 172. The end of conduit 164 opposite from the connection to theheater inlet 70 is connected to inlet port 168. The other inlet port 170is connected by a by-pass return line 176 to feed line 86 upstream fromburners 12 and 13. A check valve 178 contained in line 176 permits fluidflow only from feed line 86 to inlet port 170.

With continued reference to FIGURE 4, outlet port 172 is connected tothe inlet port of a conventional pressure regulating valve 180 by afluid conduit 182. The function of valve 180 is the same as valve 130 inFIGURE 1. The outlet port of valve 180 is connected to return line 106by a fluid conduit 184. In this embodiment, pipe section 140 isconnected to conduit 184 downstream from valve 180.

Preferably, valve 160 is a Sarco No. 58 valve as shown in the SarcoBulletin No. 620, dated January 1962, and is shown in FIGURE 5 to have avalve operating member 186 which is slidably mounted in housing 166along an axis extending at right angles to the common axis of ports 168and 170. As shown, member 186 comprises a plurality of axially spacedapart flow control pistons mounted on a common rod and is spring biasedinto engagement with a plunger 188. Axial displacement of valve member186 in one direction will proportionately open and block ports 168 and170 respectively. Similarly, displacement of member 186 in the oppositedirection will proportionately open port 170 and close port 168.

As shown in FIGURE 4, thermostatic bulb 110 is connected to control theposition of valve member 186 to thus proportion the flow of hot oilentering at port 170 and cooler oil entering at port 168. The oilentering ports 168 and 170 is mixed and discharged through port 172 forreturn to suction bell 25 through lines 184 and 186. This returnedheated oil mixes with and heats cold viscous tank oil in suction bell25, and the mixture is drawn through suction line 18 by pump set 16 andis supplied under pump pressure through heater 72 to burners 12 and 13in a manner previously described in the embodiments of FIGURES 13.

At full capacity with all of the burners operating at their maximumfiring rates under normal conditions, port 168 will be substantiallyclosed and port 170 will be proportionately open. If the heating load isreduced as by shutting down one or more of the burners or by reducingthe firing rates of any of the burners, the amount of excess hot oilreturning to suction bell 25 through line 176 will start to increase.This will result in a temperature increase in the mixture of hot andcold oil in hell 25 to cause a corresponding temperature increase in thesuction line oil. This temperature increase is sensed by bulb 110 whichdisplaces valve member 186 to respectively close and open ports 170 and168 by proportionate amounts with the result that the amount of cooleroil supplied through port 168 will increase and the amount of hot oilflowing through port 170 will proportionately decrease. As aconsequence, the temperature of oil returning to suction bell 25 throughport 172 and return line 186 will be maintained at the control settingestablished by bulb 110.

If all of the burners are shut down so that there is no load at all, nooil will be burned so that substantially all of the oil passing throughheater 72 and line 86 will return through line 176. This increases thetemperature of the oil discharged through port 172 to cause acorresponding temperature increase in suction bell 25 and suction line13. In response to this temperature increase bulb 110 shifts valvemember 186 to substantially close port 170 and open port 168 by acorresponding amount with he result that most of the oil discharged bypump set 16 through line 48 will not pass through heater 72 but ratherwill pass directly through line 164, port 168 for return to suction bell25 through line 184.

Assume now that burner 12 is operating and burner 13 is shut down andvalve 160 has automatically responded to maintain the 120 temperature insuction line 18. If burner 13 is now started up, the amount of hot oilconsumed will increase and the amount of excess hot oil returning tosuction bell 25 through line 176 will correspondingly decrease. As aresult, the temperature of the blended oil passing through port 172 willstart to decrease to cause a corresponding decrease in the temperatureof oil in suction bell 25 and in suction line 18. This temperaturedecrease is sensed by bulb 110 which displaces valve member 186 toincrease the amount of hot oil flowing through port 170 and toproportionately decrease the amount of cooler oil flowing through port168. As a result, the temperature of the oil returning to suction bell25 will be increased. Thus, it is clear that valve 160 is automaticallyresponsive to suction line oil temperature to maintain the supply oil insuction line 18 at a predetermined temperature regardless of loadconditions and the temperature setting for the oil burners.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

1. In a preheating system for heating and transporting viscous liquidfuel from a storage tank to a burner, a supply pipeline extendingbetween said tank and said burner, a pump in said line for withdrawingfuel from said tank and supplying it to said burner in predeterminedexcess of the maximum firing rate of said burner, heating means in saidline between said pump and said burner for materially raising thetemperature of pumped fuel flowing through said line to effect efircientcombustion thereof at said burner, a return pipeline connected to saidsupply line downstream from said heating means for returning heated fuelto said tank, means including temperature responsive valve meansconnected to control fuel flow through said return pipeline inverselywith respect to the temperature of supply line fuel upstream supplypipeline extending between said tank and said 1 burner, a pump in saidsupply line for Withdrawing fuel from said tank and supplying it to saidburner in predetermined excess of the maximum firing rate of saidburner, heating means in said line between said pump and said burner formaterially raising the temperature of fuel flowing through said line toefiect efficient combustion thereof at said burner, a return pipelineconnected to said supply line downstream of said heating means forreturning at least substantially all of the heated unburned fuel to saidtank in close proximity to the inlet of said supply line, flow controlvalve means connected to control the rate of fuel flow through saidreturn line, a bypass line connected to said supply line between thedischarge of said pump and said heating means for returning to said tankfuel which is diverted from said return pipeline by operation of saidcontrol valve means, and thermostatic means for controlling said valvemeans to vary the fuel flow rate through said return line inversely withrespect to the temperature of supply line oil upstream from said heatingmeans for maintaining fuel withdrawn by said pump at a predeterminedtemperature which is lower than the temperature imparted to said fuel bysaid heating means.

3. The preheating system defined in claim 2 comprising pressureregulating valve means in said bypass pipeline to maintain apredetermined fuel oil supply pressure at said burner.

4. The preheating system defined in claim 3 wherein said return line isconnected to said supply line upstream from the connection of saidburner.

5. The preheating system defined in claim 4 comprising a recirculatingpipeline connected to circulate unburned fuel from said burner to saidsupply line upstream from the connection of said return line to saidsupply line.

6. The preheating system defined in claim 3 comprising a suction bell insaid tank, the inlet and outlet respectively of said supply line andsaid return line being in said bell.

7. The preheating system defined in claim 3 comprising a purging linefor returning heated fuel from said burner to said tank and means insaid purging line for restricting fuel flow rates so as not to adverselyheat the fuel withdrawn by said pump above said predeterminedtemperature.

8. In a preheating system for heating and transport ing viscous fuel oilfrom a storage tank to an oil burner, a supply line extending betweensaid tank and said burner, a pump in said line for withdrawing fuel fromsaid tank in excess of the burner firing rate and supplying it to saidburner, heating means in said line between said pump and said burner forheating pumped oil flowing through said line to a predeterminedtemperature for effecting proper combustion, a return line havingseparate branches respectively connected to said supply line upstreamand downstream from said heating means for returning excess unburned oilto said tank, and valve means disposed in said return line and beingresponsive to the Cit temperature of the oil in said supply lineupstream from aid heating means tor automatically proportioning thenount of excess oil returned to said tank through said ranches tomaintain the supply fuel at the suction side of said pump at apredetermined temperature.

9. The preheating system defined in claim comprising means connectingone of said branches to said supply linebetween said heating means andsaid burner and the other of said branches to said supply line betweensaid pump and said heating means.

re. The preheating system defined in claim wherein said valve meanscomprises a three-way valve having a pair of inlet ports respectivelyconnected to said branches and an outlet port connected to said returnline leading to said tank.

11. The preheating system defined in claim It wherein said three-wayvalve comprises a temperature responsive valve operating member that isdisplaceable to inversely proportion the amount of oil flowing throughsaid inlets.

The preheating system defined in claim 8 comprising a suction belldisposed in said tank, the outlet end of said return line and the inletend of said supply line being disposed in said bell in close proximityto each other.

13. The preheating system defined in claim it comprising a pressureregulating valve disposed in said return line downstream from saidthree-way valve.

In a preheating system for heating and transporting viscous fuel oilfrom a storage tank and to an oil burner, a supply line extendingbetween said tank and said burner, a pump in said line for Withdrawingfuel oil from said tank inexcess of the burner firing rate and supplyingit to said burner, heating means in said line between said pump and saidburner for heating pumped oil iiowing through said line to apredetermined temperature for effecting proper combustion, a return linefor returning excess, unburned oil to said tank in close proximity tothe inlet of said supply line and including first,

eeond and third branches, said first branch being connested to saidsupply line downstream from said heating means, said second return linebranch being connected to said supply line downstream from the dischargeof said pump and upstream from said heating means, said third branchextending into said tank, valve means hav ing first and second inletports respectively connected to said first and second branches and anoutlet port connected to said third branch, means responsive to thetemperature of the oil in the supply line upstream from said heatingmeans for controlling said valve means to proportion the amount ofexcess oil returned to said tank through said first and second branchesto maintain the supply fuel oil at the suction side of said pump at apredetermined temperature, and pressure regulating valve means disposedin said third branch for maintaining a predetermined fuel oil supplypressure at said burner.

References Qited by the Examiner UNETED STATES PATENTS 2,892,520 8/57Trabilcy 158-36.0 2,876,830 3/59 Duy 158-360 3,067,809 12/ 62 Dresing.

FREDERICK L. MATTESON, IR. Primary Examiner.

ROBERT A. DUA, JAMES W. WESTHAVER,

Examiners.

1. IN A PREHEATING SYSTEM FOR HEATING AND TRANSPORTING VISCOUS LIQUIDFUEL FROM A STORAGE TANK TO A BURNER, A SUPPLY PIPELINE EXTENDINGBETWEEN SAID TANK AND SAID BURNER, A PUMP IN SAID LINE FOR WITHDRAWINGFUEL FROM SAID TANK AND SUPPLYING IT TO SAID BURNER IN PREDETERMINEDEXCESS OF THE MAXIMM FIRING RATE OF SAID BURNER, HEATING MEANS IN SAIDLINE BETWEEN SAID PUMP AND SAID BURNER FOR MATERIALLY RAISING THETEMPERAWTURE OF PUMPED FUEL FLOWING THROUGH SAID LINE TO EFFECTEFFICIENT COMBUSTION THEREOF AT SAID BURNER, A RETURN PIPELINE CONNECTEDTO SAID SUPPLY LINE DOWNSTREAM FROM SAID HEATING MEANS FOR RETURNINGHEATED FUEL TO SAID TANK, MEANS INCLUDING TEMPERATURE RESPONSIVE VALVEMEANS CONNECTED TO CONTROL FUEL FLOW THROUGH SAID RETURN PIPELINEINVERSELY WITH RESPECT TO THE TEMPERATURE OF SUPPLY LINE FUEL UPSTREAMFROM SAID HEATING MEANS TO PREVENT THE TEMPERATURE OF